1. Field of the Invention
This invention relates to N, Nxe2x80x2-substituted asymmetrical imidodicarbonimidic diamides derived from hydroxylamines and their derivatives, to a process for making them, to a pharmaceutical composition thereof and a method for protecting and/or treating a mammalian subject from infections caused by an organism selected from the group consisting of Plasmodium sp., Mycobacterium sp. and Pneumocystis carinii. 
2. Reported Developments
Malaria is an infectious febrile disease caused by protozoa of the genus Plasmodium, which are parasitic in the red blood cells, and are transmitted by the bites of infected mosquitoes of the genus Anopheles. The disease is characterized by attacks of chills, fever, and sweating, occurring at intervals which depend on the time required for development of a new generation of parasites in the body. After recovery from the acute attack, the disease has a tendency to become chronic, with occasional relapses. Among the various forms of malaria falciparum or pernicious malaria is the most serious form of malaria caused by Plasmodium falciparum, characterized by severe constitutional symptoms and sometimes causing death. The disease is prevalent in tropical and subtropical areas of the world including the Amazon region of Brazil, East and Southern Africa and Southeast Asia. Malaria has been treated with various drugs throughout recent history including combinations of drugs. While marginally successful against some strains of malaria, most strains of malaria appear to have developed resistance not only to individual drugs but also to multiple combinations of drugs. Multiple Drug Resistance, hereinafter sometimes referred to as MDR, continues to confound antimalarial drug development efforts. Drugs of diverse chemical classes, such as mefloquine, halofantrine, and artemisinin, appear to be expelled by a common transport or efflux mechanism. The mechanism of resistance to the classic antifolate antimalarials is independent of drug transport or efflux and is due to differential binding affinities to parasite dihydrofolate reductase, hereinafter sometimes referred to as DHFR, and or dihyropteroate synthase, hereafter sometimes referred to as DHPS. Efforts have been and are being made to develop DHFR inhibitors in combination with DHPS inhibitors. The efforts so far have resulted in limited success.
U.S. Pat. No. 5,322,858 to Canfield et al., which is incorporated herein by reference in its entirety, discloses N, Nxe2x80x2substituted imidocarbonimidic diamides derived from hydroxylamines, pharmaceutical formulations thereof, and methods of protecting subjects from Plasmodium sp., Mycobacterium sp. and Pneumocystis carinii by administering to a subject liable to such infection a prophylactically effective amount of said pharmaceutical formulations. The formulations are said to reduce the level of infection where said subjects have already been infected.
The patent discloses a large number of compounds in generic formula I: 
wherein:
wherein R1 is a substituted or unsubstituted divalent aliphatic group of 1 to 16 carbon atoms; wherein the substituents are mono or poly and are selected from the group consisting of lower alkyl, aryl and arlkyl, R3 is selected from the group consisting of the same group of values as R5 other than carbocycloaryl, and when further bonded to the nitrogen to which it is attached, a saturated heterocycle of 4-8 carbon atoms, R5 is selected from the group consisting of substituted and unsubstituted alkyl of 1-10 carbon atoms, aryl, cycloalkyl and heterocycloalkyl of 3-8 carbon atoms, mono or polycarbocycloaryl of 4-7 atoms per ring, wherein the substituents are; mono or poly and are selected from the group consisting of lower alkyl, cycloalkyl of 3-8 carbon atoms, lower alkenyl, lower alkynyl, nitro, lower alkoxy, lower alkoxycarbonyl, phenyl loweralkyl, phenyl, mono and polyhalophenyl, phenoxy, mono and polyhalophenoxy, and halo provided however, that such halo substitution is in a mono and polycarbocycloaryl of 4-7 atoms per ring. R6 and R7 which may be the same or different are hydrogen alkanoyl or alkoxy alkanoyl, and when further bonded to the nitrogen to which either is attached, a saturated heterocycle of 4-8 carbon atoms, and R7 may also be selected from the group consisting of same group of values as R5, and when further bonded to the nitrogen to which it is attached, a saturated or unsaturated heterocycle of 4-8 carbon atoms, Y is oxygen or sulfur, q is 0 or 1, n m is 1 or 0, having the latter value where R3 is a moiety having two bonds attached to N5, provided that unless otherwise stated the prefix alk designates moieties which are straight chain or branched chain of 1-24 carbon atoms, and when further prefixed by the term lower, designates 1-6 carbon atoms, the respective tautomers thereof, the pharmaceutically acceptable salts and addition salts thereof and the hydrates of said salts and addition salts and mono and diacyl derivatives thereof.
In testing the compounds disclosed in the patent for antimalarial activity, one candidate, identified as WR250417 or PS-15, hereinafter sometimes referred to as PS-15, was demonstrated to have significant activity against drug-resistant Plasmodium falciparum as described by Canfield et al. 1993. PS-15: A potent, orally active antimalarial from a new class of folic acid antagonists. Am J. Trop Med Hyg 49: 121-126. The compound, N-[3-(2,4,5-trichlorophenoxy)propyloxy]-Nxe2x80x2-(1-methylethyl)imidodicarbonimidediamide hydrochloride has the structure: 
The compound was found to be not cross-resistant with other inhibitors of DHFR, such as pyrimethamine and cycloguanil.
While PS-15 is similar in chemical structure to the well-known antimalarial drug 
Proguanil
it was envisioned to present a new series of antifolate drugs which were named hydroxylamine-derived biguanides. PS-15 displayed modest intrinsic antimalarial activity alone and was metabolized in vivo to WR99210, the extremely active triazine inhibitor of DHFR having the chemical structure 
When tested in vitro against drug-resistant clones of P. falciparum, it was found to be more active than proguanil, and the putative metabolite WR99210, and was found to be ten thousand times more active than the proquanil metabolite cycloguanil. PS-15 is also more active as well as less toxic than proguanil when administered orally to mice infected with P. berghei. When administered orally to Aotus monkeys infected with multidrug-resistant P. falciparum, the drug is more active than either proquanil or WR99210. Because PS-15 had intrinsic antimalarial activity, and is not cross-resistant with other DHFR inhibitors, and could be metabolized to WR99210 in vivo, oral administration of this drug was predicted to circumvent the shortcomings and retain advantages found with both proguanil and WR99210. However, development of PS-15 was stifled by environmental regulatory compliance issues which prohibited the use of required starting material, 2,4,5-trichlorophenol in bulk drug manufacturing. The synthesis of PS-15 is shown in EXAMPLE 1, U.S. Pat. No. 5,322,858.
Numerous analogs of PS-15 were prepared and several were found to have equivalent antimalarial activity. A 90-day comparative toxicity experiment showed that, with the exception of PS-26 and PS-33, PS-15 and its analogs caused testicular toxicity.
We have now synthesized a series of N,Nxe2x80x2-substituted biguanides and, unexpectedly, two of this series of N,Nxe2x80x2-subsitituted biguanides were found to be free of testicular atrophy found with the other compounds in the series. The compounds are: 1-[3-(3,4-dichlorophenoxy)propyloxy]-5-isopropylbiguanide(hemisuccinate), hereinafter sometimes designated as PS-26 
1-[3-(4-chlorophenoxy)propyloxy]-5-isopropylbiguanide(hemisuccinate), hereinafter sometimes designated as PS-33 
The compounds of the present invention are formulated with a pharmaceutically acceptable carrier for oral or injectable administration.
Oral formulations are preferred and this invention has the advantage over related products of being readily absorbed by mammals in sufficient levels to make the compounds of the present invention orally active as therapeutic agents. Formulations for oral or injected use are based on sufficient solubility as to allow the therapeutic agent to enter solution in the stomach or in an injectable medium. The drug formulations will include tablets, pills, capsules, sachets, granules, powders, chewing gums, suspensions, emulsions and solutions: particularly preferred for oral use are tablets and capsules of all varieties and microbe-free solutions for injection or infusion. Where appropriate and necessary the formulations may include diluents, binding agents, dispersing agents, surface-active agents, lubricating agents, coating materials, flavoring agents, coloring agents, controlled release formulations, sweeteners or any other pharmaceutically acceptable additives, for example, gelatin, sodium starch glycolate, lactose, starch, talc, magnesium stearate, microcystalline cellulose, Povidone, hydrogenated or unsaturated oils, polyglocols, syrups or other aqueous solutions. Where the formulations are tablets or capsules and the like the formulations may be presented as premeasured unit doses or in multidose containers from which the appropriate unit dose may be withdrawn.
The injectable form may be an aqueous or nonaqueous solution, suspension or emulsion in a pharmaceutically acceptable liquid, e.g. sterile pyrogen-free water or parenterally acceptable oils or mixture of liquids which may contain bacteriostatic agents, antioxidants or other preservatives and stabilizers, buffers (preferably but not limited to a physiological pH range of 6.5-7.7), solutes to render the solution isotonic with the blood, thickening agents, suspending agents or pharmaceutically acceptable additives. Such forms will be presented in unit dose form such as ampules or dispersable injection devices or in multi-dose forms such as a bottle from which the appropriate dose may be withdrawn, or as a solid form or concentrate which can be used to quickly prepare an injectable formulation. All formulations for injection are preferable sterile and pyrogen free. Suppositories containing the compound will also contain suitable carriers, e.g. cocoa butter, polyglycols or other state-of-the-art carriers.
In addition to standard pharmaceutical additives there may be included within formulations of the compound other therapeutic agents, particularly including other antimalarials and antiinfectives.
The preferred dosage range is between 0.5 and 10 mg/kg/day. The range is quite large because the physician must use his judgement on whether the dosage is prophylactic and if given to an infected subject, on what the level of infection is. When given as tablets the tablets may contain 25-250 mg of active material.
We have surprisingly discovered that the compounds 1-[3-(3,4-dichlorophenoxy)propyloxy]-5-isopropylbiguanide(hemisuccinate), and 1-[3-(4-chlorophenoxy)propyloxy]-5-isoproplbiguanide(hemisuccinate), have excellent antimalarial activity against infections caused by an organism selected from the group consisting of Plasmodium sp., Mycobacterium sp. and Pneumosistis carini and do not show the testicular toxicity seen with the other analogs in the series.
These compounds can be prepared by using the following general synthetic schemes for biquanides. 
Reagents: (a), 1,3-dibromopropane(for n=3), NaOH, tetrabutylammonium hydrogen sulfate; (b) AcNHOH, NaOH or KOH; alcoholic solvent (c) conc. HCl, MeOH; (d) dicyandiamide, aq. EtOH, heat and then aqeous NaOH to neutralize; (e) sodium dicyanamide, HCl, alcoholic solvent, heat; (f) EtOAc, heat; (g) HCl, MeOH, (h)RT, DMF.
Preparative methods for the compounds are described in EXAMPLES I AND II.